BLAH

1. SCIENCE CHAPTER : 9
REPRODUCTION IN ANIMALS

2.  Various modes of reproduction.
 Sexual and asexual reproduction.
 Fertilization in humans and hens.
 Internal fertilization VS External fertilization.
 Oviparous and Viviparous animals.
 Understanding Metamorphosis through the life cycle
of frog.
 Asexual reproduction in amoeba and hydra.
OBJECTIVES

3. Reproduction
REPRODUCTION IS A BIOLOGICAL PROCESS, BY
WHICH AN ORGANISM PRODUCES NEW
INDIVIDUALS OF ITS OWN KIND.
REPRODUCTION IS VERY IMPORTANT AS IT ENSURES
THE CONTINUATION OF SIMILAR KINDS OF
INDIVIDUALS, GENERATION AFTER GENERATION.

4. SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION

5. Modes of Reproduction
Sexual reproduction:
It involves the production of an individual through the fusion
of male and female gametes.
The gametes from two parents fuse to form a zygote, which
by repeated divisions gives rise to a new individual.
In animals also, males and females have different
reproductive parts or organs.
• Sexual reproduction occurs in all higher organisms.

6. Sexual Reproduction

7. Male Reproductive Organs:
• A pair of testes(singular: testis)
• Two sperm ducts
• A penis
The testes produce the male
gametes called sperms.
Millions of sperms are produced
by the testes.

8. Human Sperm
• Though sperms are
very small in size, each
has a head, a middle
piece and a tail.
• Each sperm is a single
cell with all the usual
cell components.

9. Female Reproductive Organs:
• A pair of ovaries
• Oviducts (fallopian tube)
• Uterus
✔The ovary produces female
gametes called ova (eggs).
✔In human beings, a single matured
egg is released into the oviduct by
one of the ovaries every month.
✔Uterus is the part where
development of the baby takes place.

10. Human Ovum
⮚The size of eggs in animals varies.
⮚The egg may be very small as in
humans, much larger as in
hens.
⮚Ostrich egg is the largest cell.

11. Fertilization:
The process of fusion of the egg and the
sperm is called fertilization.
Two types of fertilization are:
1. Internal fertilization
2. External fertilization

12. External fertilization • During spring or rainy season, male and female
frogs come together in water.
• The female lays hundreds of eggs.
• Unlike hen’s egg, frog’s egg is not covered by a
shell and it is comparatively very delicate.
• A layer of jelly holds the eggs together and
provides protection to the eggs.
• As the eggs are laid, the male deposits sperms
over them.
• The sperms come in contact with the eggs and
this results in fertilization.
The type of fertilization in which the fusion of a male and female gamete takes
place outside the body of the female is called external fertilization.
Eg: Fish, Starfish, Frog etc.

13. Why do fish and frogs lay eggs in
hundreds whereas a hen lays only
one egg at a time?
• Though these animals lay hundreds of eggs and release millions of
sperms, all these eggs do not get fertilized and develop into new
individuals.
• This is because the eggs and sperms get exposed to water
movement, wind and rainfall.
• Also, there are other animals in the pond which may feed on eggs.
• Thus, production of large number of eggs and sperms is necessary
to ensure fertilization of at least a few of them.

14. Fertilization in humans
• Fertilization occurs in the oviducts or fallopian tubes.
• Since fertilization takes place inside the body of human female in the
oviducts, it is called internal fertilization.
• Internal fertilization occurs in many animals including humans, cows, dogs
and hens.

15. • During fertilization, the nuclei
of the sperm and the egg
fuse to form a single nucleus.
• This results in the formation
of a fertilized egg or zygote.
• The zygote is the beginning of
a new individual.
• Zygote is a single cell with a single nucleus having
hereditary material of both mother and father.
• After the formation of zygote, a protective layer gets formed
outside the zygote.
Fertilization in humans

16. Development of Embryo • Fertilization results in the
formation of zygote which begins
to develop into an embryo.
• The zygote divides repeatedly to
give rise to a ball of cells.
• The cells then begin to form
groups that develop into different
tissues and organs of the body.
• The developing structure is
termed an embryo.
• The embryo gets embedded in
the wall of the uterus for further
development.

17. • The embryo continues to
develop in the uterus.
• It gradually develops body parts
such as hands, legs, head, eyes,
ears etc.
• The stage of the embryo in
which all the body parts can be
identified is called a foetus.
• When the development of the
foetus is complete, the mother
gives birth to the baby.

18. Difference between and Zygote and Foetus
Zygote Foetus
It is formed by the fusion of the
nuclei of the sperm and egg.
It is the stage of the embryo which
nearly resembles a human being.
It is a unicellular structure. It is a multicellular structure.
Produced after the processes of
fertilization.
Produced after the processes of cell
division and cell labour division.
In Zygote, well-described body are
absent.
In Foetus, well-described body
parts are present.

19. Test Tube Babies and In Vitro Fertilization
(IVF)
Sometimes due to medical reasons or due to blockage of oviducts, the
fertilization of an ovum and sperm does not occur and so the woman
is not able to bear a child. In such cases IVF technique helps.
• IVF is technique in which the eggs from a female are taken out and
fertilized with the sperm outside the body in a glass disc or a glass
tube.
• The fertilized ovum or zygote is allowed to develop into an embryo for
about one week.
• One week after fertilization, the embryo formed is placed back into the
mother’s body in the uterus and its further development takes place
in the uterus till birth.
• The babies conceived through IVF technique are commonly called
test tube babies.

20. Development
of Chick
• Internal fertilization takes place in hens.
• Soon after fertilization, the zygote divides repeatedly and travels down the oviduct.
• As it travels down, many protective layers are formed around it.
• After the hard shell is formed around the developing embryo, the hen finally lays the egg.
• The embryo takes about 3 weeks to develop into a chick.
• Mother hen sits on the eggs to provide sufficient warmth. The development of the chick
takes place inside the egg shell during this period.
• After the chick is completely developed it bursts open the egg shell.

21. Internal Fertilization VS. External Fertilization

22. Viviparous and Oviparous Animals
Oviparous

23. Difference between Oviparous and Viviparous Animals

24. The transformation of the
larva into an adult
through drastic changes is
called metamorphosis.

25. Life Cycle of Frog
Egg Tadpole (Larva) Adult
https://www.youtube.com/watch?v=FIXoJYb
Bls0

26. Life cycle of frog

27. Modes Of Reproduction
• Asexual Reproduction
✔The type of reproduction in which only a single parent is involved is
called asexual reproduction.
✔It gives rise to individuals that are identical to the parent.
✔Gametes are not formed and so there is no fertilization.

29. Binary Fission in Amoeba
https://www.youtube.com/watch?v=ReX0r2vm2U8

30. Budding in Hydra
https://www.youtube.com/watch?v=d5-hPkcQDrU

31. Story of Dolly, the Clone
Cloning is the process of generating genetically identical copy of a cell
or an organism.

33. Let’s Summarize: